The goals of this research proposal are 1) to identify polymorphic loci from DNA adjacent to telomeres of individual human chromosomes, and to use them in linkage studies to attempt closure of the genetic maps, and 2) to identify and place on the linkage maps polymorphic loci for individual human centromeres, providing useful chromosome reference points for both genetic and physical mapping. Human telomere-specific and centromere-specific Yeast Artificial Chromosome (YAC) clones as well as other probes for centromeres and candidate telomere adjacent sequences will be provided as starting materials by collaborators. Chromosomal localization of the telomere and centromere probes will be determined by 4 hybridization to telomere-specific and centromere-specific sequences, and by genetic linkage analysis. We plan to construct libraries from the centromere and telomere YAC clones, screen them for probes that reveal polymorphism, genotype the 40 CEPH reference pedigrees, and integrate the markers into our genetic maps using the linkage analysis program package CRI-MAP. In addition, we will genotype existing centromere-specific probes and existing telomere adjacent probes on reference pedigrees and make use of centromeric genotypic data provided by our collaborators, enabling us to incorporate these previously identified RFLPs into the maps. For any telomere RFLP that does not link to the genetic map (a map that by all other criteria should span the chromosome), YAC walking experiments will be conducted in an effort to link the physical end of chromosome with the genetic map. The proposed research, which has only recently become feasible, will define the boundaries of genetic maps and facilitate merging of physical and genetic maps. We will also develop efficient data management systems for tracking of resources and data within our laboratory, for communication with other laboratories, and for contributing large data sets to established national resource databases.